WO2011116498A1 - Fluororesin sheet - Google Patents

Abstract

A fluororesin sheet and the preparing method thereof are provided. Said fluororesin sheet, which costs less and has high compression rate, is characterized in that it is prepared from the composition designed for sheet making, including (A) fluororesin, (B) fillers without perlite, (C) perlite and (D) processing aid.

Description

 Fluororesin sheet technical field

 The present invention relates to a fluororesin sheet. Background technique

 The fluororesin is filled with a filler to form a sheet-like sheet, and not only the chemical resistance and heat resistance of the fluororesin but also the properties* inherent to the filler or the resistance of the fluororesin are improved. The disadvantage of creep, and more for sealing materials.

 As a sheet of the present invention, a method for producing a fluororesin sheet comprising a fluororesin, a filler, and a processing aid has been disclosed in Japanese Laid-Open Patent Publication No. 2007-253519 (Patent Document 1). As the filler, clay or the like can be mentioned. According to this production method, it is possible to obtain a fluororesin sheet which is compatible with high resilience and high sealing property and which is suitable for a gasket material.

 However, since such a fluororesin sheet tends to be a hard sheet having a small compression ratio, when the sheet is used as a gasket or the like, it is necessary to obtain a predetermined sealing property under high-pressure tension. Further, as described above, in the case where the sheet is hard, there is still room for further improvement due to poor workability of the sheet into a desired shape of the sheet or the like.

 Patent Document 1: Japanese Laid-Open Patent Publication No. 2007-253519 SUMMARY OF INVENTION

 The present invention has been made in view of the above problems, and an object thereof is to provide a fluororesin sheet which has a large compression ratio under low pressure and is excellent in workability and low in cost.

 The present inventors conducted intensive studies to solve the above problems, and as a result, found that a sheet made of a composition containing a fluororesin, a filler (excluding perlite), perlite, and a processing aid is inexpensive. The compression ratio is large, and the sealing property equivalent to or better than that of the conventional product can be obtained under a low pressure, and the workability in which the sheet is punched into a desired shape or the like is also good, and the present invention has been completed.

The specific structure of the present invention is as follows. The fluororesin sheet of the present invention is characterized by comprising: (A) a fluororesin, (B) a filler (excluding perlite), (C) perlite, and (D) a processing aid for sheet formation. The composition is manufactured.

 The content of the (C) perlite in the above composition is preferably 4 to 20 parts by weight relative to 100 parts by weight of the total of (A) fluororesin, (B) filler (excluding perlite), and (C) perlite. .

 In addition, in the following description, the "filling material" referred to means a filling material excluding perlite.

 The content of the (D) processing aid in the above composition is preferably 5 to 50 by weight with respect to 100 parts by weight of the total of (A) fluororesin, (B) filler (excluding perlite), and (C) perlite. Share. Effect of the invention

 The fluororesin sheet of the present invention can be produced at low cost by using (C) porous structure perlite and (B) other fillers, for example, in combination with clay.

 According to the present invention, it is possible to obtain a fluororesin sheet which is excellent in secondary workability in the shape of a gasket or the like, and has a large compression ratio under a low pressure, and exhibits a good seal even when used under a low pressure. Sex. detailed description

 The invention is described in further detail below.

 [Fluororesin sheet]

 The fluororesin sheet of the present invention is characterized by: a sheet for forming a sheet containing (A) fluororesin, (B) filler (excluding perlite), (C) perlite, and (D) processing aid. The composition is manufactured.

 < (A) Fluoro Resin >

As the above (A) fluororesin, polytetrafluoroethylene resin (PTFE), modified PTFE, polyvinylidene fluoride resin (PVDF), tetrafluoroethylene-ethylene copolymer resin (ETFE), chlorotrifluoroethylene resin can be preferably used. A fluororesin which has been conventionally known as (PCTFE), tetrafluoroethylene-hexafluoropropylene ethylene copolymer resin (FEP), and tetrafluoroethylene-perfluoroanthryl copolymer resin (PFA). Among them, from the aspects of processability in extrusion molding, rolling, etc. As the polytetrafluoroethylene resin (PTFE), a PTFE ultrafine powder obtained by emulsion polymerization is particularly preferable. Since the PTFE ultrafine powder has a property of fibrillation under the action of shearing force, the (B) filler material can be obtained in the process of each component in the stirring and mixing composition described later, and in the process of forming the sheet. Further, (C) a composition and/or a sheet composed of perlite or the like, whereby a fluororesin sheet excellent in sealing property and mechanical strength can be obtained.

 In the case of using PTFE as the above (A) fluororesin, the fluororesin may contain a small amount of a fluororesin other than the above PTFE, for example, 10% by weight or less (the total weight of the fluororesin is 100% by weight) or less.

 As the fluororesin (A), a powdery fluororesin may be used as it is, or a dispersion obtained by dispersing fluororesin fine particles in water may be used.

 < (B) Filling material>

 As the (B) filler, the following (C) perlite is not included, and carbon-based fillers such as graphite, carbon black, expanded graphite, activated carbon, and carbon nanotubes may be used depending on the purpose; talc, mica, clay, An inorganic filler such as calcium carbonate, magnesium oxide, silicon carbide, aluminum oxide or silica; or a powder of a resin such as PPS. Further, as the (B) filler, a fiber material having a fiber length of 10 mm or less composed of carbon fiber, aramid fiber, or asbestos may be used.

 According to the present invention, even when (A) the filling rate of the fluororesin is low and (B) the filling ratio of the filler is high, a fluororesin sheet having a large compression ratio can be obtained. The weight ratio of the above (A) fluororesin and the above (B) filler (excluding perlite) is preferably 1: 0.1 to 3, more preferably 1: 0.1 to 2.

 When the filler (B) is contained in the above content, a fluororesin sheet having sufficient properties of the filler can be obtained.

 < (C) Perlite >

(C) above perlite is silica (Si0 ₂₎ high content of foam volcanic rock system, consisting of silicon dioxide (SiO ₂ 70~80%), alumina (A1 ₂ 0 ₃ 10~20 %) and Na ₂ 0, K ₂ 0 (total 0 to 10%). Examples of the volcanic rock are perlite, obsidian, and rosin. In the present invention, a foam of any of the above rocks may be used, and perlite having a porous structure and excellent oil absorption rate is particularly preferable.

Such (C) perlite is extremely light in weight, excellent in heat insulation, and inexpensive and non-flammable. Thus, an inexpensive fluororesin sheet suitable for use at high temperatures can be obtained. Further, since (C) perlite is excellent in liquid absorbing property, it is considered in the present invention that it can absorb the (D) processing aid in the composition for sheet formation. Therefore, when a sheet is formed from a composition for sheet formation, in the case of the following method (I), the (D) processing aid is impregnated and held in the perlite in the rolling step. Most of the holes. Therefore, in the rolling process, the pore structure of the perlite is not easily collapsed, and in the subsequent drying step, the (D) processing aid is volatilized, and the obtained sheet retains voids (pores) in the perlite. Therefore, in particular, a fluororesin sheet having a large compression ratio and an appropriate sealing property under a low pressure tightness can be obtained.

 In the composition for sheet formation, relative to (A) fluororesin, (B) filler (excluding perlite), and (C) perlite ((A) + (B) + (C) The amount of the above (C) perlite is preferably 4 to 20 parts by weight, more preferably 5 to 8 parts by weight, per 100 parts by weight.

 Further, in the obtained fluororesin sheet of the present invention, the amount of (C) perlite is the same as described above with respect to (A) + (B) + (C) = 100 parts by weight.

 Further, the average particle diameter of (C) perlite (measured by a laser particle size distribution analyzer) is preferably 150 μm or less, more preferably 75 to 125 μm.

 When (C) perlite is contained in the above amount, and the average particle diameter of the (C) perlite is within the above range, a fluororesin sheet which maintains high sealing property and has a large compression ratio can be obtained.

 If in the composition for sheet formation, a total of 100 parts by weight relative to (Α) fluororesin, (Β) filler (excluding perlite), and (C) perlite, the above (C) perlite When the amount is 5 to 8 parts by weight, a fluororesin sheet having properties such as low compression ratio, high sealing property, high tensile strength, and low stress relaxation property can be obtained, which is preferable.

 < (D) Processing Aids >

 The (D) processing aid is not particularly limited, and a known processing aid such as a petroleum hydrocarbon solvent, ethanol, water or the like can be used.

As a commercial product of a petroleum hydrocarbon solvent, for example, Isopar C manufactured by ExxonMobil (internal organic solvent, fractionation temperature: 97 to 104 ° C), Isopar G (hydrocarbon organic solvent, fractionation temperature: 158) can be cited. ~175 ° C ) and Isopar M (hydrocarbon organic solvent, fractionation temperature: 218 to 253 ° C). As an industrial solvent having characteristics such as n-hexanide, low benzene ring number, and low aromatic solvent, Japan Energy CACTUS SOLVENT R5N manufactured by Corp. The (D) processing aid may be used in the production of a fluororesin sheet in the case of the following method (I), as long as it may contain an appropriate amount of processing aid after the rolling step; In the sheet-formed composition, the amount of the processing aid (D) is preferably 5 with respect to 100 parts by weight of the total of (A) fluororesin, (B) filler (excluding perlite), and (C) perlite. It is -50 parts by weight, more preferably 10 to 40 parts by weight. When the (D) processing aid is used in the above amount, the blended raw material can be easily uniformly mixed and dispersed, and the sheet made of the obtained composition is excellent in workability. When the fluororesin sheet is produced, when the following method (I) is employed, the fluororesin can be sufficiently swollen in the initial stage of the rolling step to be described later, and before the firing step described later, The processing aid is not completely volatilized, so that the rolled sheet containing an appropriate amount of processing aid is obtained.

 Essentially, the composition for sheet formation consists only of the above (A) fluororesin, (B) filler, (C) perlite, and (D) processing aid.

 In the preparation of the composition for sheet formation containing the above components, the above components may be added to the container in a single order or in small portions at a time, stirred, mixed, or the like.

 The stirring and mixing method is not particularly limited as long as it corresponds to the composition of the fluororesin sheet to be produced, and is blended with (A) a fluororesin, (B) a filler, (C) perlite, and (D) a processing aid. Stir and mix in any order. When the stirring efficiency is not good, a processing aid can be added, and after the stirring is completed, excess processing aid is removed by filtration.

 Further, the temperature at the time of mixing and mixing is preferably a temperature which is lower than the temperature of the roll in the rolling process without volatilizing the processing aid.

 [Method of Manufacturing Fluororesin Sheet]

 The method for producing a fluororesin sheet of the present invention is not particularly limited as long as it can form a fluororesin sheet from the composition for forming a sheet, and a conventionally known method can be employed. Preferably, the above method is employed. The composition for sheet formation is preformed, and the obtained preform is rolled at a roll temperature of 40 to 80 ° C, and then dried and fired (hereinafter also referred to as method (I)).

 The method (I) is specifically described below.

 [Method (I)]

The method (I) includes a pre-forming step, a rolling step, a drying step, and a baking step in this order. <Preforming process>

 In the preforming step, the above composition for forming a sheet is extrusion molded to obtain a preform (extruded product).

 The shape of the preform is not particularly limited, but a rod shape or a belt shape is preferable in consideration of the subsequent sheet formation efficiency, the uniformity of the sheet shape, and the like.

 In the production method of the present invention, the preforming step is preferably carried out at a temperature at which the processing aid is not volatilized and is lower than the roll temperature in the rolling step.

 <Rolling process>

 In the rolling step subsequent to the pre-forming step, the preform is rolled into a sheet shape by rolling between rolling rolls represented by a biaxial roll.

 In the production method of the present invention, the rolling step is carried out at a roll temperature of 40 to 80 °C. If the roll temperature is within the above range, the hardness of the (A) fluororesin is slightly lowered, and the fluororesin sheet is more easily densified. Moreover, (D) the processing aid is not completely volatilized.

 If the rolling step is carried out at a temperature lower than 40 °C, the processing aid tends to be difficult to volatilize. On the other hand, when the rolling is carried out at a temperature exceeding 80 °C, the above-mentioned (D) processing aid is excessively volatilized, and there is a tendency that a fluororesin sheet containing a filler having a large compression ratio cannot be formed. In addition, since the processing aid (D) is excessively volatilized, the processing aid remaining in the initial stage of the rolling process is reduced. Therefore, the fluororesin which is not sufficiently swollen (A) fluororesin and which is not fibrillated can be obtained. The tendency to be inferior. Further, since the (D) processing aid in the composition is rapidly vaporized to cause swelling, the sealing property of the fluororesin sheet tends to be lowered.

 Further, in the production method of the present invention, the step of further rolling the rolled sheet produced by the rolling step described above is repeated, that is, the rolling step is repeated a plurality of times (for example, 3 to 50 times). Since an appropriate amount of processing aid remains in the sheet after the rolling step, it is preferred to appropriately adjust the number of rolling. Further, when the rolling process is repeated, the roll pitch is made narrower every time the rolling is repeated.

 When the preform is rolled into a sheet by a biaxial roll, for example, the roll pitch is set to 0.5 to 20 mm, and the roll surface moving speed (sheet extrusion speed) is 5 to 50 mm/sec. body.

 <Drying process>

In the drying step, the sheet after the rolling is placed at a normal temperature or at a small temperature. The processing aid is removed by heating at the temperature of the melting point of the fluororesin.

 <Burning process>

 In the baking step, the dried sheet is heated at a temperature equal to or higher than the melting point of the fluororesin to be sintered. As the heating temperature, it is considered that it is necessary to uniformly burn all the sheets, and a fluorine-based harmful gas is generated at an excessively high temperature, and although there are some differences depending on the type of the fluororesin, for example, 340 is appropriate. ~370 ° C.

 [Fluororesin sheet]

The fluororesin sheet is not particularly limited as long as it is produced from the above composition for forming a sheet, and it is preferred to produce the sheet by the above method (I). The fluororesin sheet is inexpensive and has a large compression ratio. Specifically, the compression ratio is preferably 7% or more, more preferably 8% or more, and the upper limit thereof may be 15%; leakage amount (sealing test, for The test piece having a thickness of 1.5 mm and a thickness of 1.5 mm is preferably 7.0 x 10' ³ Pa «m ³ /s or less, and further preferably 2.0 x 10 ^ 3 - m ³ under conditions of a surface pressure of 19.6 MPa and a nitrogen internal pressure of 0.98 MPa. Below /s, the lower limit value may also be 1.0x10 - ⁵ Pa · m ³ /s.

 The fluororesin sheet of the present invention as described above can be used in a gasket, and the gasket made of the fluororesin sheet of the present invention can be used at a high temperature (for example, at 200 ° C or higher) for a long period of time, even at a low pressure. A gasket with high sealing properties can also be obtained.

 The above gasket can be easily produced by punching the fluororesin sheet of the present invention into a desired shape. The fluororesin sheet of the present invention is easy to punch and has high processability.

[Examples]

 The invention is further illustrated by the following examples, but the invention is not limited to the examples.

 <Test method>

 A test piece was prepared from a sheet having a thickness of 1.5 mm, and the sealing property was measured as described below. Leakage (sealing)

A gasket test piece punched into a size of Φ 48 mm x Φ 67 mm was installed between steel flanges of Φ lOOmmx height 50 mm and surface roughness Rmax = 12 m, and the surface pressure was 19.6 MPa (200 kg by compressing the test machine). Cm ² G). The internal pressure was 0.98 MPa (1.0 kg^cm ² G) from the through hole for pressure introduction provided on the flange to the inner diameter side of the gasket, and then the pressure was introduced into the pipe for 1 hour. Pressure sensor The pressure change before and after the hold is read, and the amount of leakage is obtained from the pressure drop value.

 Stress relaxation

 The stress relaxation rate at 100 °C and 200 °C was measured based on the ASTM F38 B method.

 Compression ratio

 The compression ratio was measured based on ASTM F36.

 Tensile Strength

 Tensile strength was measured based on JIS R3453. [Embodiment 1]

 PTFE (CD-I, manufactured by Asahi Glass Co., Ltd.): 17.1kg,

 Micro-powder clay (XN-D325, manufactured by Anhui Xuena Non-Metal Materials Co., Ltd.): 9.6kg,

 Perlite (average particle size ΙΟΟμιη, manufactured by Qingdao Yuzhou Chemical Co., Ltd.): 1.7kg, hydrocarbon organic solvent (Isopar G, manufactured by ExxonMobil): 7.5kg After mixing for 15 minutes at room temperature with a kneader, It was allowed to stand at room temperature (25 ° C) for 16 hours to be aged, and a composition for sheet formation was prepared.

 The composition was extruded at room temperature (25 ° C) using an extruder having a metal port of 300 mm x 20 mm to prepare a preform.

 The preform was rolled by a twin-axis roll under the conditions of a roll diameter of 700 mm, a roll pitch of 20 mm, a roll speed of 6 m/min, and a roll temperature of 70 °C. Immediately after the rolling, the obtained sheet was again rolled at a roll pitch of 10 mm. Subsequently, the obtained sheet was rolled five times with a gradually narrower roll pitch of 8 mm, 6 mm, 4 mm, 2 mm, and 1.5 mm to obtain a sheet having a thickness of 1.5 mm.

 The sheet was allowed to stand at room temperature (25 ° C) for 24 hours to remove the processing aid, and then fired in an electric furnace at 350 ° C for 3 hours to obtain a fluororesin sheet.

The leakage of the fluororesin sheet (sealing) is 2.1xl0_ ⁵ (also written as = 2.1E-05)

Pa · m ³ /s, the compression ratio is 9%.

[Embodiment 2]

A fluororesin sheet was produced in the same manner as in Example 1 except that the composition of the composition for sheet formation used in Example 1 was changed as shown in Table 1 below, and the roll temperature was changed to 80 °C. The leakage (sealing property) of the fluororesin sheet is UxlO Λ-4

 ^ Pa ^ m s, compression ratio

10%.

[Embodiment 3]

 The composition for sheet formation used in Example 1 was changed as shown in Table 1 below, and extruded at room temperature (25 ° C) with an annular die extruder having an outer diameter of 300 mm and an inner diameter of 260 mm. A fluororesin sheet was produced in the same manner as in Example 1 except that a preform was formed.

The leakage amount (sealing property) of the fluororesin sheet is

The compression ratio is 9%.

[Embodiment 4]

 A fluororesin sheet was produced in the same manner as in Example 3 except that the composition for sheet formation used in Example 3 was changed as shown in Table 1 below.

The leakage amount (sealing property) of the fluororesin sheet is SJxlO^Pa · m ³ /s, and the compression ratio is

10%.

[Comparative Example 1]

 A fluororesin sheet was produced in the same manner as in Example 1 except that the composition for sheet formation used in Example 1 was changed as shown in Table 1 below.

The leakage amount (sealing property) of the fluororesin sheet was 1.1 lx (T ⁴ Pa * m ³ / _S , and the compression ratio was

6%.

[Comparative Example 2]

 A fluororesin sheet was produced in the same manner as in Example 1 except that the composition for sheet formation used in Example 1 was changed as shown in Table 1 below.

The leakage amount (sealing property) of the fluororesin sheet is

Compression ratio

4%. Table 1

 EXAMPLES EXAMPLES EXAMPLES Comparative Examples Comparative Examples Project Unit

 1 2 3 4 1 2

CD-I kg 17.1 17.1 15.6 15.6 13.3 17.1

XN-D325 kg 9.6 9.1 9.4 7.7 15 11.3 Perlite (average particle size

 Kg 1.7 2.27 3.4 5.1 0 0 ΙΟΟμπι)

 Isopar G kg 7.5 9.4 8 9.4 8.6 7.5 Seal test No coating seal

Pa-m ³ /S 2.10E-05 1.1E-04 6.20E-04 5.3E-04 1.1E-04 1.1E-04 Glue

Compression ratio % 9 10 9 10 6 4 Tensile strength MPa 18 15.6 13 10 17.7 15.6 Stress relaxation 100°C % 28 33 34 30 29 37 Stress relaxation 200°C % 46 55 51 50 48 66

Claims

Claim

A fluororesin sheet characterized by:

 It is produced from a composition for sheet formation containing (A) a fluororesin, (B) a filler which does not include perlite, (C) pearlite, and (D) a processing aid.

2. The fluororesin sheet according to claim 1, wherein:

 The content of the (C) perlite in the composition is 4 to 20 parts by weight based on 100 parts by weight of the total of (A) the fluororesin, (B) the filler which does not include perlite, and (C) the pearlite.

3. The fluororesin sheet according to claim 1, wherein:

 The content of the (D) processing aid in the composition is 5 to 50 parts by weight relative to 100 parts by weight of the total of (A) fluororesin, (B) filler material excluding perlite, and (C) perlite. .